Under Gravel Filter Cleaning Help

[waterdrop]

A couple of us have been trying to help another TFF member with a temporary undergravel filter problem. I don't use one myself (although I did, some, years ago, so I understand them) and don't have answers that are sufficient.

Background: One (or probably more) undergravel filters were in the user's 80G/300L tank when it was acquired and were left in place. The filter grids have debris under them, possibly from many years of use. The user has stocked this tank with fish and is planning to acquire a new external cannister filter a couple of weeks from now and begin fish-in cycling it, after which they plan to dismantle the undergravel filter at some point. The questions pertain to this several week period prior to the new cannister being cycled and running (not trying to start a ugf pro/con discussion here) .

Question1) Would sucking out all the debris from under the grids cause her a worse problem (the tank is already un-cycled and is receiving water changes.)

Question2) Where do the nitrifying bacteria reside in a ugf system? My assumption is attached to the substrate gravel above the filter grid and also some on the plastic grid itself, but I might be wrong here and a significant load of them might reside in the debris itself, so what do we think?

Question3) Somebody (CFC, Bignose, Colin, ? can't remember who) wrote that pressing a siphon hose up against the grid (after pushing gravel away) and then watching until all the black debris clears out through the hose will do the trick. Is this true? Any comments?

Question4) Somebody else made the interesting comment that one could devise an adapter, attach it to the corner pipes of the ugf system, attach the other end to a wet/dry vacuum and suck out all the dirt with high speed (sounded wild but there you have it!) Any experiences anyone?

Question5) Finally, and to possibly state question1 a different way: Which would be worse, mucking with ugf to clean it or not mucking with it, continuing to run it or not running it (I believe there is no other filter on the tank)

OK, there, in all their muddy glory, are the questions I can think of that might help this person! Best Regards, ~~waterdrop~~

 

[waterdrop]

Gee, no takers for the UK evening hours? I'm surprised.

 

[backtotropical]

Question1) Would sucking out all the debris from under the grids cause her a worse problem (the tank is already un-cycled and is receiving water changes.)

If there is any chance that this debris is laced with bacteria (mulm as we call it), then it would make the situation significantly worse if removed. If however the debris has been left to dry out in the transition of ownership of the tankand the bacteria have died, it will be serving no purpose other than polluting the tank, probably with ammonia, and should be removed as soon as possible. There would be only positive effect in doing this as no bacteria would be removed, only toxin generating waste.

I can't advise any more specifically as i don't know what happened to the tank in the transition between owners, and therefore if there is a chance of any bacteria being alive.

Question2) Where do the nitrifying bacteria reside in a ugf system? My assumption is attached to the substrate gravel above the filter grid and also some on the plastic grid itself, but I might be wrong here and a significant load of them might reside in the debris itself, so what do we think?

The bacteria reside mainly in the substrate in a UGF system. It is the same as any other filter setup in that the bacteria will live on the glass of the tank, on the decor etc etc, but as the vast majority of the bacteria live on the filter media in say, an external filter, the live on the substrate in a UGF system.

The plastic grid will have bacteria living on it, but a nominal amount as with the aquarium glass etc. The main colony is in the gravel due to the surface area available.

Just as with any other filter, a significant amount of bacteria will live on the debris, but in this case, as i mentioned above, it will depend entirely on the events between ownerships and whether any bacteria have been retained.

Question3) Somebody (CFC, Bignose, Colin, ? can't remember who) wrote that pressing a siphon hose up against the grid (after pushing gravel away) and then watching until all the black debris clears out through the hose will do the trick. Is this true? Any comments?

I'm not sure what this would achieve that just gravel vaccing wouldn't. Gravel vaccing is an essential part of a UGF system, just as rinsing the sponge etc is a vital part of keeping an external working properly, as it avoids dead spots which the bacteria will not inhabit.

Question4) Somebody else made the interesting comment that one could devise an adapter, attach it to the corner pipes of the ugf system, attach the other end to a wet/dry vacuum and suck out all the dirt with high speed (sounded wild but there you have it!) Any experiences anyone?

Never experienced it or heard of it being done. I suppose it could work, but gravel vaccing would achieve the same result without sucking the fish out the tank.

Question5) Finally, and to possibly state question1 a different way: Which would be worse, mucking with ugf to clean it or not mucking with it, continuing to run it or not running it (I believe there is no other filter on the tank)

If the UGF has any bacteria colony whatsoever, it should undoubtedly be left in place. If there are bacteria in it, keep cleaning to a minimum, as with any other filter. If there are no bacteria populating the filter system, remove the filter and all the debris as they will only pollute the water.

I think the main issue here appears to be establishing whether there are any established bacteria left in the UGF system. If there are, leave it in and run the new external along-side it for 6 weeks and then remove the UGF (piece by piece if possible). If there are no bacteria left in the filter system, get rid of it.

All that said, the best solution in this case appears to be to return all the fish and start a fishless cycle with the new external. It would be a lot less heartache.

Anyway, hope this helps.

Cheers

BTT